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Initial dual flight training for the Airplane-Private Pilot rating in the USA requires a dual control aircraft with a certificated Flight Instructor for the class of aircraft-in this case-Single-Engine Land.
All unmodified stock Beech 35/36s have a single throw-over control wheel for control of the ruddervators or conventional tail models which in this aircraft control both the elevator and the rudder turn functions as well as angle of incidence climb or descent in vee-tail or conventional tail Bonanzas. It is understood that coordinated use of the Beech 35 wing ailerons and ruddervators is necessary for coordinated flight maneuvers. Straight tail Bonanzas also have a standard throw-over control wheel unless modified by STC.
The single throw-over control wheel Beech 35/36s are specifically prohibited in the FARs for learning to fly a single engine-land aircraft, UNLESS an approved STC for installation of true dual control wheels has been installed in that aircraft.
A Flying Club I was in in the late 1960s in Southern California with nine varied aircraft had a stock 35 Bonanza that the owner after joining had specifically had modified with true dual controls per Supplemental Type Certificate so that SEL pilots could be checked out in the aircraft legally with an airplane-SEL Flight Instructor. That A&P STC installation made that Bonanza then legal to train SEL pilots to check out in the Bonanza with an appropriate Flight Instructor. It was never used for any initial flight training as the Club had C140s and C150s for that. I used a Piper PA-28 180 in the Club for pleasure flights and the cheaper reimbursement C150s for my frequent business flights in California, as I had earlier learned to fly on six PA-28-140s.